The genus Lobelia includes approximately 375 species of annuals, perennials, shrubs or sometimes trees, native mostly to tropical and warm temperate regions. Irregular tubular flowers and an acrid, milky latex characterizes them. Several herbaceous species are popular in flower gardens and thrive in moist, shady and semi-shady locations. Within the genus, foliage color ranges from light green to bronze green and bronze red and habits from trailing to upright. Flower color ranges from blue, violet, red, yellow or white and is often bicolor (Hortus Third A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Company (1976)).
Cultivated species include: Lobelia erinus, a small annual herb, native to southern Africa that bears blue or violet flowers; Lobelia cardinalis, a tall, perennial herb commonly called cardinal flower bearing vertical clusters of large, crimson flowers; Lobelia siphilitica, the commonly called blue cardinal flower; Lobelia splendens, commonly known Mexican Lobelia, similar to Lobelia cardinalis with the major difference being bronze leaves; and Lobelia inflata, known for production of the alkaloid lobeline, used medicinally Id.
Many popular cultivars, including ‘Bees Flame’ and the Fan Series, have been produced from interspecific hybridization of Lobelia splendens, Lobelia cardinalis, or Lobelia siphilitica. Collectively these hybrids are known as Lobelia×hybrida. Lobelia×Gerardii, a hybrid resulting from a cross between L.×‘Queen Victoria’ and L. siphilitica, produces flowers that are often larger than other Lobelia species in a range of colors from pink to violet purple (Ball Perennial Manual Propagation and Production, Ball Publishing (1996)).
Interspecific hybrids identified as L.×speciosa are the result of crossing Lobelia siphilitica and Lobelia cardinalis. These hybrids whether naturally occurring or artifical show many intermediate morphological characteristics of the two parents. Many tetraploid hybrids of L.×speciosa have been produced through intercrossing spontaneous tetraploids and/or those produced using colchicine treatments (W. Bowden. Canadian Journal of Botany 60: 2054-2070 (1982)).